In a rolling process of a flat-rolled metal material, it is very important to roll a sheet material in a form free from camber, or in a form not having bend in the left-right direction, in order to avoid not only a plane shape defect and a dimensional accuracy defect of the rolled material but also to avoid sheet pass troubles such as a zigzag movement and a tail crash.
Further, a warp that occurs at the time of rolling a sheet material also has a large influence on productivity of products, such as reduction in rolling efficiency and increase in the number of refining processes. For example, as for the refining processes, there are cases where it is necessary to correct camber or a warp using a leveler or by performing pressing or the like, and in an extreme case, a defect part may have to be cut. Still further, in the case where camber or a warp occurred to a large extent, the rolling facility may be damaged due to the collision of the sheet. In this case, it is not only that the sheet itself loses the product value, but that it brings about tremendous damages such as production interruption and repairing of the rolling facility.
In addition, in order to control the above camber with high accuracy, it is also important to perform an initial setting called zero point adjustment. The zero point adjustment is performed as follows: kiss-roll tightening is conducted by operating a screw down device in a roll-rotating state; and, a point in which a measurement value of a rolling load corresponding to a preset zero point adjustment load (preset to rated load of 15% to 85%) is set as a zero point of a reduction position, and the reduction position is set as a starting point (reference) in reduction control. In this case, the difference between left and right reduction positions, that is, the zero point of reduction leveling is often adjusted simultaneously. Also, as for the zero point adjustment of the reduction leveling, the measurement values of the rolling load on the time of kiss-roll tightening on the operator side and the driving side are adjusted such that the measurement values correspond to the preset zero point adjustment load. Note that the kiss-roll tightening means that, under the state that a rolled material is not present, the upper and lower work rolls are brought into contact with each other and a load is applied between the rolls.
Incidentally, to simplify expressions, the operator side and the driving side of the rolling mill, as the right and left sides when the rolling mill is seen from the front of the rolling direction, will be referred to as “right and left”, respectively.
In view of the problems attributed to such camber, Patent Document 1 suggests a rolling method and a rolling apparatus capable of stably producing a flat-rolled metal material free from camber or having an extremely light camber. Specifically, in the rolling method and the rolling apparatus described in Patent Document 1, a load detection device measures a rolling direction force acting on roll chocks on an operator side and a driving side of a work roll, and a calculation device calculates a difference of the rolling direction forces between the operator side and the driving side. Then, a control device controls a left-right swivelling component of a roll gap of a rolling mill such that the difference becomes zero.
In view of the problem of a warp, Patent Document 2 suggests a rolling method and a rolling apparatus capable of stably producing a flat-rolled metal material having an extremely light warp. Specifically, in the rolling method and the rolling apparatus described in Patent Document 2, load detection devices provided on both entry side and exit side of upper and lower roll chocks of work rolls measure rolling direction forces acting on the upper and lower work roll chocks. Then, a calculation device calculates a difference between the rolling direction force on the upper side and the rolling direction force on the lower side, that is, an upper and lower rolling direction force difference. After that, upper and lower asymmetric components of the rolling apparatus is controlled such that the upper and lower rolling direction force difference is decreased.
In view of the problem of zero point adjustment, in Patent Document 3, it is discovered that a rolling direction force occurs even with zero point adjustment by the kiss roll state, pointed out that the rolling direction force does not affect a roll thrust force, and accordingly, there is proposed a method enabling more precise initial reduction position adjustment (reduction zero point adjustment) of a rolling mill.
Further, in order to produce a flat-rolled metal material free from camber, in a rolling method and a rolling apparatus described in Patent Document 4, rolling direction forces acting on roll chocks on an operator side and a driving side of a work roll are measured, a difference of the rolling direction forces between the operator side and the driving side is calculated, a left-right swivelling component of a roll gap of the rolling mill is controlled by using control gain such that the difference become a control target value, and the control gain is changed depending on a condition during rolling.
Still further, Patent Document 5 suggests a rolling mill and a rolling method capable of producing a flat-rolled metal material free from camber or warp, achieving zero point adjustment with high accuracy, and easily achieving application of a strong roll bending force. In the rolling mill and the rolling method described in Patent Document 5, a work roll chock is pressed against a contact surface with a housing window or a project block of the rolling mill in a rolling direction. Then, a load detection device measures rolling direction forces acting on roll chocks on an operator side and a driving side of a work roll, and a calculation device a calculation device calculates a difference of the rolling direction forces between the operator side and the driving side. A control device calculates left-right swivelling component control quantity of a roll gap of the rolling mill such that the difference become a control target value, and controls the roll gap on the basis of the calculated value of the left-right swivelling component control quantity of the roll gap.
Here, in any of the rolling methods and the rolling apparatuses described in the above Patent Documents 1 to 5, the rolling direction forces are measured. Accordingly, with reference to FIG. 1, the measurement of the rolling direction forces according to Patent Documents 1 to 5 will be described specifically. FIG. 1 is a view schematically showing a rolling apparatus.
The rolling apparatus shown in FIG. 1 includes an upper work roll 1 supported by an upper work roll chock 5, an upper backup roll 3 supported by an upper backup roll chock 7, a lower work roll 2 supported by a lower work roll chock 6, and a lower backup roll 4 supported by a lower backup roll chock 8. The upper backup roll 3 is disposed on the upper side of the upper work roll 1 in contact with the upper work roll 1. In the same manner, the lower backup roll 4 is disposed on the lower side of the lower work roll 2 in contact with the lower work roll 2. Further, the rolling apparatus shown in FIG. 1 includes a screw down device 9 that applies a rolling load to the upper work roll 1. A flat-rolled metal material M to be rolled by the rolling apparatus moves in a rolling direction F between the upper work roll 1 and the lower work roll 2.
Though FIG. 1 basically shows only the apparatus construction on the operator side, similar devices exist on the driving side, too.
The rolling direction force acting on the upper work roll 1 of the rolling apparatus is basically supported by the upper work roll chock 5. Between the upper work roll chock 5 and a housing or a project block, there are provided an upper work roll chock exit side load detection device 121 on an exit side of the upper work roll chock 5 in the rolling direction, and an upper work roll chock entry side load detection device 122 on an entry side of the upper work roll chock 5 in the rolling direction. The upper work roll chock exit side load detection device 121 can detect the force acting between the member such as the housing or the project block and the upper work roll chock 5 on the exit side of the upper work roll chock 5 in the rolling direction. The upper work roll chock entry side load detection device 122 can detect the force acting between the member such as the project block and the upper work roll chock 5 on the entry side of the upper work roll chock 5 in the rolling direction. To simplify the device construction, those load detection devices 121 and 122 preferably and ordinarily have a construction for measuring a compressive force.
The upper work roll chock exit side load detection device 121 and the upper work roll chock entry side load detection device 122 are connected to an upper work roll rolling direction force calculation device 141. The upper work roll rolling direction force calculation device 141 calculates a difference between a load detected by the upper work roll chock exit side load detection device 121 and a load detected by the upper work roll chock entry side load detection device 122, and, on the basis of the calculation result, calculates the rolling direction force acting on the upper work roll chock 5.
In the same manner, as for the lower work roll 2, between the lower work roll chock 6 and the housing or the project block, there are provided an lower work roll chock exit side load detection device 123 on an exit side of the lower work roll chock 6 in the rolling direction, and a lower work roll chock entry side load detection device 124 on an entry side of the lower work roll chock 6 in the rolling direction. The lower work roll chock exit side load detection device 123 and the lower work roll chock entry side load detection device 124 are connected to a lower work roll rolling direction force calculation device 142. The lower work roll rolling direction force calculation device 142 calculates, on the basis of measurement values obtained by those load detection devices 123 and 124, the rolling direction force acting on the lower work roll chock 6 in the same manner as in the upper work roll 1.